In many roofing systems, metal or wood trusses are used to support roof assemblies and/or to support the roofing systems. Trusses may include a variety of support members such as, for example, a top chord, web members, a bottom chord, and/or other members. Typically, the top chord is supported by a number of web members that extend from a bottom chord. A number of trusses may be placed on a building frame in a parallel spaced-apart arrangement. As such, the slope of the top chords can define the pitch of a roof. Additional support members, sometimes referred to as purlins, may be incorporated into roofing systems as well.
The purlins can be disposed at or on top of the top chords of the trusses top chords. The purlins can be arranged in a spaced-apart arrangement. The purlins also can be arranged in a direction perpendicular to the top chords. As such, the purlins can help support downward loads of roof assembly and/or can provide support for roofing system members between the trusses, if desired.
The use of purlins and/or trusses as discussed hereinabove can be particularly useful for supporting weight of roofing systems that incorporate heavy and/or dense members such as, for example, barrel roof tiles, stainless steel roofing systems, and/or other roofing systems. The purlins also can be used to help provide ventilation for a roofing system. More particularly, the purlins can be used to create a gap or air space between the trusses and roofing panels or other roofing structures. Providing gaps or air spaces such as those provided by purlins can help extend the life of roofing systems, can provide spaces to accommodate insulation, and/or can be beneficial for other reasons.
Purlins come in various shapes, dimensions, and/or can be formed from various materials. In particular, purlins may include dimensional lumber, formed sheet metal with right angle bends having one of several shapes. Purlins generally include a surface onto which roofing panels or other members can be mounted, and legs or webs that support the mounting surface. The legs or webs can be arranged perpendicular to the mounting surface and/or at an angle to provide structural support and/or to provide eased shipping, stacking, and/or other manufacturing processes. The purlins also can include mounting feet or webs with which the purlins are connected to the trusses or other roofing system members.
Such purlins may be used to meet certain determined roofing system performance requirements. For example, purlins can be designed and/or selected to provide vertical resistance to dead loads as required by various building codes and/or as specified by architectural, engineering, and/or other design specifications. The performance of the purlins and/or the entire roofing system can depend upon a variety of factors, including, but not limited to, the type, thickness, and spacing of the trusses and roof panels, as well as the type and placement of fasteners used to assemble the roofing system. Such performance is measured by a variety of organizations that test roof assemblies.
It is with respect to these and other considerations that the disclosure made herein is presented.